Electrical switching devices, for example circuit breakers or molded case circuit breakers, in particular have the task of decoupling one or a number of consumers in the event of a fault in a voltage supply network. Conventional types of fault here are the occurrence of a short circuit or the occurrence of an overcurrent. A thermomagnetic overcurrent detection unit is often used in the electrical switching devices, being embodied to trip in the event of a short circuit and in the event of an overcurrent, thereby ensuring decoupling from the voltage supply network.
When such a thermomagnetic overcurrent detection unit is used, it is however not easy for the user to determine the reason for the fault responsible for tripping the electrical switching device. The user is not given any information about whether a short circuit or an overcurrent has caused the isolation of the power circuit. To determine the reason for the fault, it is therefore necessary to examine the subordinate power circuit for possible causes.
If no obvious short circuit is found, the user will in particular assume an overcurrent to be the reason for the thermomagnetic overcurrent detection unit of the electrical switching device tripping. However if this judgment is wrong and a short circuit that is not obvious was the reason for the electrical switching device tripping, reactivation of the electrical switching device can have fatal consequences for the user. The short circuit still present in the subordinate power circuit means that the thermomagnetic overcurrent detection unit will trip again immediately. Disadvantageous consequences for the user, even injury, can result.
An insertable indicator switch module for an electrical switching device configured as a switch, in particular a low voltage circuit breaker, is known from DE 10 2010 022 596 A1, indicating the reason for tripping when the electrical switching device trips in the event of a short circuit. Since this indicator module, which can in particular be retrofitted, is only activated when a fault is due to a short circuit, said reason is also indicated to the user in the event of a short circuit. The user of the electrical switching device is therefore informed that there is a short circuit in the subordinate power circuit.
The user trusts that a short circuit in the subordinate power circuit can reliably be indicated as the reason for the electrical switching device tripping by such an indicator switch module. In the case of an electrical switching device which has been retrofitted with such an indicator module in particular, the user cannot however be certain that the indicator module and the electrical switching device interact in the intended manner.